The present invention relates to applicators which are used for medical purposes such as administering a medication to an animal for mastitis and, more particularly, to an applicator having a partial insertion cannula for limiting the depth of the insertion of the cannula during the administration of the medication.
Bovine mastitis is a problem which afflicts a large number of dairy cows. This mastitis is an inflammation of the cow""s mammary gland and has a detrimental effect on milk production and profitability of a farm dairy operation. Treatment of bovine mastitis has typically been accomplished by administering various antibiotic compositions into an animal""s udder through a teat canal.
Initially, mastitis infusion syringes were provided from the antibiotic supplier as a molded plastic, disposable unit having a single piece plastic cover which typically snap-fitted onto the hub of the syringe at the base of the cannula to cover the cannula prior to use. The protective cap was removed at the time of treatment from the cannula and the cannula end inserted into the cow""s teat end, passed up through the teat canal and positioned within a teat cistern. After being correctly positioned, the treatment antibiotic is injected from the syringe directly into the cow""s teat cistern.
Studies have shown that full cannula insertion through the teat canal can have detrimental effects on the effectiveness of the mastitis treatment. Research has shown that in some instances, bacteria infecting the keratin lining of the teat canal can be carried into the teat cistern by the mastitis cannula during the full insertion thereof to produce mastitis.
A cow""s teat canal is approximately 5 to 10 mm in length and has a very narrow lumen of about 0.4 to 1.63 mm. This narrow canal helps prevent bacteria from entering a cow""s udder. Although some bacteria may survive in the keratin lining and secretions in the distal teat canal, they are prevented by the healthy teat canal from traveling the full length of the canal. During full cannula insertion, these bacteria can be aided in their travel of the teat canal by the cannula. It has also been discovered that the teat canal or duct keratin layer, which helps control bacterial penetration into the udder, may be damaged by full cannula insertion. Full cannula insertion also may cause the full length of the teat canal lumen to dilate and allow increased bacterial travel and penetration into the teat cistern and mammary gland.
In order to avoid the above problems, a partial insertion technique has been developed wherein the mastitis cannula is inserted into the teat end of the teat canal only to a depth of generally about 3-4 mm. Although this technique is beneficial in the treatment of mastitis, it has made the treatment procedures more difficult and time consuming for the dairyman out in the field. This technique requires that the cannula insertion depth be limited to generally about 3-4 mm to avoid teat canal keratin damage, dilating of the entire teat canal and preventing the transport of bacteria from the distal teat canal into the teat cistern. In order to fulfill this need, Ennis, III et al, U.S. Design Pat. No. Des 308,724, discloses a short mastitis cannula.
Ennis, III et al, U.S. Pat. No. 4,981,472, also discloses a cannula assembly for injecting medicinal fluid into an animal""s teat comprising a first tapered cannula. Second and third cannulas can be provided to provide the user with a choice of cannulas of three different lengths for insertion into a teat.
Manchester, U.S. Pat. No. 5,053,020, discloses an applicator for administering medication comprising a syringe cylinder having a first reduced diameter, blunt-tipped cannula integral with and projecting therefrom. A second cannula of reduced diameter and also having a blunt tip is detachably mounted on the base of the first cannula to offer the user a choice between partial and full insertion of the cannula.
Sutherland, U.S. Pat. No. 5,059,172, discloses a syringe with a two part mastitis cannula cap comprising an outer cap and an inner cap. The inner cap is not as long as the cannula so that a free end of the cannula can protrude beyond an end face of the inner cap. Controlled depth partial insertion of the cannula into the teat canal of a dairy cow can be accomplished by removal of only the outer cap. Alternatively, full depth cannula insertion can be accomplished by removing both parts of the cap.
Although the above patents provide methods for partial and full insertion of a cannula, they require manual manipulation of cannulas or caps provided on the cannulas in order to afford the desired administration technique. This increases the risk of contamination and makes the administration of the medication unnecessarily complicated. As such, there is a need for a mastitis treatment applicator which can administer a medication by either partial or full insertion which minimizes the risk of contamination and does not require extensive physical manipulation.
According to the invention, there is provided a method of using an applicator for administering a medication in which the applicator comprises an elongated syringe having an integral blunt-tipped cannula extending longitudinally from an end thereof. The cannula has a longitudinally extending bore and comprises a first portion for partial insertion of the cannula and a second portion for complete insertion of the cannula with an annular ridge provided between the cannula first portion and cannula second portion for limiting the partial insertion of the cannula. A detachable protective cap can be provided over the cannula to protect the contents of the syringe from contamination and sealing the cannula against leakage. The annular ridge serves as an indicator for the insertion depth of the cannula in order to obtain partial insertion. If it is desired to have full insertion, the diameter of the cannula is sufficiently small so that the cannula second portion can be completely inserted into the teat canal of an animal.